Hitherto, as paper material sheets such as wallpaper, ceiling paper or liner for plywood, especially fusuma paper or shoji paper in a Japanese style house or liner for paintings and calligraphic works, there are known a rewettable fusuma paper or wallpaper having a water-soluble paste as coated and dried thereon, a so-called tacking type adhesive sheet composed of a paper sheet base coated with a release paper via an adhesive therebetween, and a so-called ironing type adhesive sheet.
The above-mentioned water-soluble paste-coated rewettable fusuma paper or wallpaper is prepared by previously coating a water-soluble paste, which is naturally coated to the back surface of said fusuma paper or wallpaper with a brush or roll just before applying the paper to a fusuma or wall, followed by drying the coated paste thereon in the step of forming the fusuma paper or wallpaper. In assuring a smooth and even adherence of the water-soluble paste-coated rewettable fusuma paper or wallpaper to a fusuma or wall, the amount of water to be applied to the paper for rewetting has a great influence on the finished condition. If the amount of water applied thereto is too small, the paper will adhere to the surface of a fusuma or wall before the wrinkles in the paper formed during sticking operation have been stretched out, so that the adhered paper is affixed with wrinkles. On the other hand, if the amount of water applied is too large, the wrinkles formed during the sticking operation could well be stretched but, when the paper base is made of pulp or a similar water-absorbing sheet, the sheet will shrink and draw back the four edges of the sheet before adhesion. As a result, the area of the paper in the finished state is reduced. Fusuma paper that is applied to fusuma in such a way will leave a paperless space between the fusuma paper and the fusuma frame, which is unfavorable. Similarly, the shrunken wallpaper as applied to a wall causes paperless gaps in the paper-to-paper joint area, which are also unfavorable. The amount of water to be applied to a rewettable fusuma paper or wallpaper of the kind varies, depending upon the ambient humidity, so that adjustment of the amount of water to be applied thereto requires high-level of skill.
A so-called tacking type fusuma paper or wallpaper is a means of avoiding the difficult watering process involved in the above-mentioned rewettable fusuma paper or wallpaper. Application of such tacking type fusuma paper or wallpaper to a fusuma or wall is effected by peeling the release paper previously applied to the back surface of the paper so that, with the finish of the sticking operation, the papering of the fusuma or wall is finished. This tacking type fusuma paper or wallpaper has various advantages in that the sticking operation is effected rapidly and that the operating environment is not messy as no water is needed for sticking. However, it has drawbacks in that, since re-sticking is impossible, the stuck paper is often wrinkled and the paper itself is high-priced.
An ordinary ironing type fusuma paper includes a modified type of the above-mentioned rewettable fusuma paper where only the four edges of the paper are dried with a household iron during sticking, and a fusuma paper sheet having a heat-sensitive adhesive laminated or coated on the back surface thereof. The advantages of the former are that the stuck paper hardly wrinkles even if an excess amount of water has been applied to the rewettable fusuma paper, as the peripheral edges of the wetted paper are dried and stuck with an iron. Also the area of the applied paper is not reduced. However, as it needs watering, it has various drawbacks in that the number of operating steps is complicatedly more than with the ordinary rewettable paper and that the operating environment becomes dirty.
The latter heat-sensitive adhesive laminated or coated sheet is one as prepared by laminating or coating a heat-sensitive adhesive onto the back surface of a fusuma paper sheet which is used in an ordinary rewettable fusuma paper, by roll coating or lamination. It is said to have various advantages in that it may easily be stuck without deframing the fusuma, without water and by anyone with a few tools. Sticking may also be effected rapidly because of the characteristic dry adhesion. In fact, however, it has various drawbacks in that it must be stuck only to an evenly planed surface, that it cannot be stuck to a fusuma having an uneven or rough surface, that when it is stuck to a fretwork fusuma, the shade of the inner frets would appear if sticking is effected under too much pressure, and that since no water can be used in sticking, the paper would be elongated to cause wrinkles or swollen areas even though a water mist is applied thereto in sticking. Because of these reasons, only a dry iron can be used. No steam iron can be used, even though it is known that a steam iron is effective for stretching wrinkles out of the paper sheet and for rapid sticking of the paper.
In particular, in the conventional heat-adhesive paper sheet, since the paper material itself is naturally applicable by sticking with a water-soluble paste, application of water thereto causes increase of the water content to result in elongation of the paper sheet, while decrease of the water content by drying results in reduction of the same. Therefore, in sticking with an ordinary iron, there occurs still another drawback in that the water content in the paper material decreases during sticking under heat to yield wrinkles, while the water content therein increases after completion of sticking and the size of the stuck paper is enlarged to cause swelling in the area of the paper with sticking failure.
Therefore, the surface to which a conventional heat-adhesive paper sheet is stuck must be thoroughly planed and flat so that uniform pressure may be applied by ironing, and a high-temperature ironing is needed for the sticking.
The object of the present invention is to provide a heat-adhesive paper sheet, which may be well applied even to an object having an uneven surface, which may be stuck with a steam iron, which may have a good surface condition after sticking, and which may accurately be stuck even at a relatively low temperature in a short period of time.